A syringe used in medical procedures usually consists of an outer chamber of cylindrical shape containing a plunger or piston movable in the chamber by manual manipulation of an actuator which projects from the piston to the exterior of the chamber. The chamber of the syringe ends in a body portion called a hub which carries a hollow needle called a cannula having an interior passage called a lumen. The needles usually have a sharpened point to facilitate the percutaneous insertion. These syringes may be used to draw in a liquid medication by withdrawal of the piston in the chamber and inject the medication intravenously into a vein by moving the piston into the chamber. Inversely, the syringe may be used to insert into a blood vessel for the purpose of withdrawing blood samples for diagnostic test purposes.
The syringe also has a function in biopsy procedures. Most biopsy procedures are accomplished by inserting a hollow tube (cannula) into an area to be tested. The targeted tissue moves into a side recess in the cannula and a second knife-like sleeve moves over the recess to incise the tissue and trap it in the cannula so it can be removed for inspection by a pathologist.
Within the last decade, a new biopsy procedure has been receiving acceptance. It is referred to as the "skinny" needle technique and is particularly useful in obtaining biopsy samples deep within the body. If an X-ray or mammogram shows an area which appears to be suspect, the "skinny" needle in the form of a very thin tube, perhaps seven-tenths of a millimeter in diameter, can be inserted into the area to be checked. This technique can be used for checking areas within a breast, in the lung, in the pancreas, in the liver, in the prostate, in the thyroid, in lymph nodes and other area deep within the body. The insertion causes minimal trauma to the patient and is generally done in cooperation with an X-ray technician (radiologist) who assists in the directing of the end of the thin needle to the area targeted. Measurements made from X-rays or pictures obtained by ultrasound determine the angle of the thrust and the depth of penetration of the needle.
The present invention is especially pertinent to this fine needle technique since once the needle has reached the sensitive area, a vacuum is drawn on the inner passage of the needle to draw in cells to be studied under a microscope. Thus, the fine needle is attached to the hub of the syringe and guided into the patient. A withdrawal of the syringe plunger draws the cells into the end of the needle which is then withdrawn from the patient. A problem exists when the applied suction continues aspirating unwanted cells or fluids as the needle is withdrawn. It is not practical to push in the plunger for fear of discharging the vital tissue sample. The present invention is directed to a means of relieving the negative pressure (suction) in a manner which is controlled by the operator and requires only a quick and simple finger manipulation at the syringe.
The object of the invention is accomplished by an attachment to a syringe hub of a secondary hub carrying the needle. An annular device such as an O-ring is mounted on an annular groove in the secondary hub and this groove has a port in communication with the interior of the hub. Normally, this ring seals the port but a slight rolling of the ring opens the port to atmosphere and relieves the negative pressure. Then the needle can be withdrawn safely carrying the desired specimen in the end.
Other objects and features of the invention will be apparent in the following description and claims in which the principles of the invention are set forth together with details to enable persons skilled in the art to practice the invention, all in connection with the best mode presently contemplated for the invention.